As if in defiance of the cliché, we usually can judge a book by its cover — or at least determine enough information about its substance to discern at a glance whether it might be worth reading. The bestsellers by the cash registers at Walmart, squat paperbacks bearing familiar names like Michael Connelly or Danielle Steel, are designed to convey a reassuring simplicity to readers wary of the exotic; the stock photographs and boldface letters, signs of safe harbour amid literature’s vast uncharted seas. Yet what attracts many to a run-of-the-mill potboiler or Harlequin romance will deter those more discriminating, who avoid, by instinct, books whose pedigree seems nearer the airport than the library. Each of us can sense, in even the colour scheme of a cover, if the writing it binds is likely to accord with our tastes. This prejudice is an invention of publishers and their marketing departments. But among books, appearances rarely deceive.

The cover of Penguin’s paperback edition of The Perfect Nanny is archetypal of a certain kind of popular fiction. It depicts the ominous upper torso of a woman of indeterminate age, “elegant in her blouse,” as she is described in the book, with its “sky-blue Peter Pan collar.” The title — invented by the publisher for the American translation — is embossed in a deep navy foil, gleaming when it catches the light. Kate Hamer, credited as “bestselling author of The Girl in the Red Coat,” is quoted, extolling the book as “insanely good,” while a strapline in upper-case crimson announces that it is the “#1 International Bestseller.” It could not be mistaken for anything other than a mainstream thriller — some hackneyed procedural, we assume uncharitably, bristling with routine violence and suspense. Our imaginations provide the missing expression, sure to be appended in a later printing: Now a Major Motion Picture. Amazing with this cover it isn’t yet.

Author Leila Slimani.Catherine HÈlie Gallimard/Penguin Random House

In Paris, where the Moroccan-born author Leila Slimani lives with her husband and two young children, The Perfect Nanny still bears its original title, Chanson Douce, which means “sweet song” or “lullaby.” (It is available as Lullaby in Great Britain.) Because book design in France has a stark uniformity, itlooks, in common with all books in that country, like serious literature: spartan tan background, conservative serif typeface, tasteful red double border. In 2016, when Slimani was awarded the Prix Goncourt — the most prestigious literary honour in France, whose past winners include Marguerite Duras, André Malraux and Marcel Proust — the book was reissued with a red banner flaunting these laurels, its most brazen display of commercial avarice.

However, because Slimani’s bleak and brilliant novel has enjoyed a degree of success rare among highbrow writers — in France, within its first year in print, Chanson Douce sold 600,000 copies, an extraordinary coup — its publisher feels obliged to promote it in North America as an accessible, mass-market hit. This effort is facilitated by the nature of the subject, derived by the author from a real-life cause célèbre. In 2012, two children, ages six and two, were stabbed to death with kitchen knives in their family’s Upper West Side apartment by their nursemaid. It was a hideous scandal that inspired the sort of headlines that appall and spellbind; the sort that might attract a journalist such as Slimani, observing cooly from across the Atlantic. And yet The Perfect Nanny is not a work of sensationalism. The novel’s first sentence disabuses the reader of such false impressions so swiftly and emphatically that it has already become famous: “The baby is dead.” No tension. No tingle of shameful thrill. A grim inevitability hangs over all that follows, as we feel that every page, every paragraph, will only lead back to this sobering end, to this atrocity flatly preordained. The baby is dead. There is nothing exciting about it.

If it is the object of the popular novel’s early pages to entice readers, it sometimes seems The Perfect Nanny aspires to do the opposite. It is hostile to the kind of readers to whom it is being marketed. A difficult novel in the guise of a popular one, it is virtually guaranteed to disappoint. The book’s Goodreads infamy is legendary. A profile of Slimani in The New Yorker written when The Perfect Nanny was published in the U.S. last January sifts through criticism on the social book-review site and concludes that it is “for some people, a nonstarter,” including one user who “gave the book a single star, recalling that she’d wondered if the pages had been bound out of order.” Many on Goodreads echo the sentiment. “I wish the author made this more comprehensible, easier to understand,” complains another one-star pan. “The only question is WHY but we never know WHY and the question of WHY remains unanswered throughout the whole book until the end.”

The Perfect Nanny is what you would call a character study. It is about two women, Myriam and Louise, yoked together intimately, precariously, as employer and employee. The relationship between these two women — Myriam the mother of two, back to work as an industrious lawyer after a stultifying entr’acte as caregiver to the kids; Louise, the hired help, “a miracle worker,” as Myriam and her husband Paul praise her to their friends, whose arrival makes them feel “as if they’ve been blessed” — is freighted with the difference in status that inherently divides them. Slimani is interested in class where a writer of mere thrillers would be interested only in psychology. Class defines and animates these characters, informs their attitudes and their motivations; class creates friction, even enmity, and if she stops short of blaming Louise’s barbarous crimes on social inequality — absolution she doesn’t deserve — Slimani nevertheless makes us aware, uneasily, of how central money and power are to all of our lives. Class, Slimani reminds us, determines fates both tragic and benign.

Slimani is very good at making you feel very bad.

Does this sound too academic? The Perfect Nanny is dissatisfying, deliberately, but it is not without simple pleasures. Slimani is very good at making you feel very bad. In a few stark lines, she can invoke some indelible dread or menace, and find in the banal some elusive threat lurking. Toward the end of the novel, as we brace ourselves for the inevitable, Myriam, oblivious to what’s impending, must confront Louise about her more extreme household economies. “The nanny scrapes out the last morsels from jam jars; she makes the children lick out their pots of yogurt,” Slimani writes. “The nanny collects coupons and proudly presents them to Myriam, who is ashamed to find this behaviour idiotic.” Myriam and Paul tease Louise in private over her inordinate thrift. But the niggardliness soon gets to be too much, and Myriam, fearing the influence on her kids, issues an edict: “She refuses to let Louise give the children food that is past its expiration date.”

Louise says nothing. But when she retaliates, it is unforgettably upsetting. Myriam returns home from the office one night, kids already in bed, house spotless, when “she sees it. There, in the middle of the little table where the children and their nanny eat. A chicken carcass sits on a plate. (…) Glistening … without the smallest scrap of flesh hanging from its bones,” the chicken looks “as if it’s been gnawed clean by a vulture,” devoured with scrupulous abandon. Myriam, at first bewildered, “stares at the brown skeleton, its round spine, its sharp bones, its smooth vertebrae. Its thighs have been torn off, but its twisted little wings are still there, the joints distended, close to breaking point. The shiny, yellowish cartilage resembles dried pus. Through the holes, between the small bones, Myriam sees the empty insides of the thorax, dark and bloodless. No meat remains, no organs, nothing on this skeleton that could rot, and yet it seems to Myriam that it is a putrescent carcass, a vile corpse that is festering and decaying before her eyes, here in the kitchen.”

Myriam is certain. That chicken was in the trash: she threw it away herself that very morning. “The meat was no longer edible; she didn’t want her children getting ill from it.” The smell had alone “made her feel sick.” Later Myriam confronts her daughter about it — she doesn’t dare confront Louise. The child, happy, explains “how Louise had taught them to eat with their fingers,” and instructed her and her brother to scratch away at the bones. “The meat was dry and Louise let them drink big glasses of Fanta as they ate, so they wouldn’t choke.” Vivid, and horrifying, and cleverly in harmony with the principal theme — the corpse of the chicken a nauseating reminder of incompatible values, of comfort and desperation, excess and need. Louise exacts a petty revenge against Myriam for her privilege. She weaponizes her waste, and if we are disturbed, it is in part because we recognize our own wastefulness, and fear retribution. Of course it doesn’t stop with rotting food. Before this ends, there will be more corpses.

As with her second novel, she drew from the news for inspiration, but again, what appealed to her about the story is not what you might think.

In the spring of 2011, Slimani was sitting on the couch in her Paris apartment, watching the news on TV. Dominique Strauss-Kahn had just been arrested in New York following allegations that he had sexually assaulted a hotel maid. Pundits, aroused to comment by the peculiarity of the case, speculated about sex addiction, and in the days that followed, Slimani read about this intriguing disease. What struck her most about these pieces was the disparity: “None of them were about women,” she said in an interview with the Irish Times. So she started doing some research. “I read psychiatric books and went on internet chat sites where sex addicts tell each other about their suffering, like drug addicts or alcoholics,” she explained. The result was Dans le Jardin de l’Ogre, or In the Garden of the Ogre. Slimani’s first novel, published when she was 34. It won the Prix La Mamounia, largely felt to be the Moroccan equivalent of the Prix Goncourt.

In the Garden of the Ogre is about sex addiction the way that The Perfect Nanny is about a murderous nursemaid. As with her second novel, she drew from the news for inspiration, but again, what appealed to her about the story is not what you might think. The book is certainly salacious — it concerns a woman whose fixation on sex is obsessive, fanatical — but like The Perfect Nanny, it brazenly resists convention, preferring to be obstinate and aggressive in lieu of likeable. “She was the one who asked for it,” Slimani writes of the hero, Adèle, the morning after an all-night tryst. “She thought she could take it. Five times, maybe ten, he lifted up his leg and his sharp, bony knee smashed into her vulva.”

Adèle, in common with her author, is a journalist in her 30s. She is married, a mother, with ambitions, vague but restless, to do more, anything more. Slimani writes of her contempt for work and family, her rock-depth apathy, with a candour that must make her real-life husband wince. More painful to read of than Adèle’s masochistic escapades with lovers unknown are the endless mundane days she endures in the company of the unremarkable people who love her, surgeon partner Richard and infant son Lucien.

On the subject of domesticity, Slimani can be ruthless. “She looks at them and realizes that her life will always be the same now.” After a romantic dinner during a holiday at the beach (“now she wants to vomit”), they sleep together, husband and wife, for the first time in she can’t remember how long (“probably last summer”), the same as always (“no foreplay”). The despair rendered at the end of this episode is as harrowing as the violence in The Perfect Nanny: “She felt nothing, nothing at all. She just heard the sounds they made, like a toilet plunger: torsos sticking, genitalia bumping. And then, a vast silence.” A debut, the book suffers in comparison to The Perfect Nanny, whose technique is more sophisticated and writing more refined. But it is a serious, severe novel, accomplished and thoughtful, with characters well-realized, themes developed intelligently.

In the wake of The Perfect Nanny’s success, In the Garden of the Ogre has only recently arrived to North America, newly translated into English. The striking paperback from Penguin depicts a faceless brunette with bare shoulders and a Louise Brooks haircut, out of focus and dim. The title — it is being released here as Adèle — is embossed in striking scarlet foil, lipstick-rich. The cover strapline, perched in clear white letters above the upper-case name Leila Slimani, are five words meant to herald another hit: “Bestselling Author of The Perfect Nanny.”